Many of today's most common consumer products, such as hand held computers, personal digital assistants, cellular telephones, and digital cameras, rely on flip chip technology to meet the demands of function versus space. Many of these devices have to perform flawlessly in adverse environmental conditions. A primary enemy of flip chip technology is heat. A flip chip integrated circuit may be held in place by hundreds of solder interconnects that provide an electrical and thermal interface to the system in which it is installed.
Problems can occur in flip chip devices if the coefficient of thermal expansion (CTE) of the surrounding package or board doesn't exactly match the CTE of the flip chip device and the solder interconnects. The corners and edges of the flip chip may move slightly due to the heat. This slight movement may cause extremely large pressures on the solder interconnects and in some cases may cause cracks that can cause failure of the flip chip integrated circuit. The occurrence of these cracks is called delamination.
The delamination typically occurs in the thin outer layers of the integrated circuit that form the foundation for the solder interconnects. The delamination may cause cracks that increase the probability that the integrated circuit will fail. It exposes the design to conditions far beyond the original design goals. This excursion into uncharted performance areas may cause the integrated circuit to operate but misinterpret data or transfer erroneous information.
Many strategies have been developed in order to live with delamination. The outermost interconnects in an array may be reserved for ground connections while the inner most interconnects may be the data to operate the function. This allows giving up some interconnects as a sacrificial barrier. This type of strategy may extend the useable life of an integrated circuit, but cannot prevent the eventual demise of the flip chip integrated circuit. While giving a sense of good design, this strategy leaves the reliability of the flip chip integrated circuit at the mercy of heat and the delamination process.
Thus, a need still remains for a means to resist the cause of delamination and extend the reliability of the flip chip integrated circuit. In view of the growing demand for integrated circuit devices packed full of our favorite functions in smaller and smaller spaces, it is increasingly critical that answers be found to these problems. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations, and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to save costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.